C++ Lesson 02: Classes and Objects
2.1 struct in C++
In C++, the struct is expanded to contain not only data (variables) but also functions. All the data and functions can be assigned to different access sections: private, protected, and public. It has the same capabilities as a class except that. By default, a structure's members are public. The general form of a C++ structure is:
struct class_name : inheritance_list {
public:
// public members by default
protected:
// private members that can be inherited
privated:
// private members
} object_list;
The class_name is the type name of the structure, which is a class type. The individual members are referenced using the dot (.) operator when acting on an object or by using the arrow (->) operator when acting through a pointer to the object. The object_list and inheritance_list are optional.
New struct in C++
#include <stdio.h>
#include <iostream>
using namespace std;
typedef struct STUDENTINFO{
private:
int age;
string name;
public:
void SetAge(int a);
void SetName(string n);
void PrintInfo();
} STUDENTINFO;
//------------------------------------------------------------------------------
int main()
{
STUDENTINFO Student;
string name;
int age;
age = 16;
name = "Ryan";
Student.SetAge(age);
Student.SetName(name);
Student.PrintInfo();
return 0;
}
//------------------------------------------------------------------------------
void STUDENTINFO::SetAge(int a)
{
age = a;
}
void STUDENTINFO::SetName(string n)
{
name = n;
}
void STUDENTINFO::PrintInfo()
{
cout << "Name: " << name << endl;
cout << "Age: " << age << endl;
}
//------------------------------------------------------------------------------
2.2 Classes and Objects
C++ creates a new user-defined data type — class. It similar to the struct, but there are still some differences between both, we will discuss it in the 2.4 section.
A class is a basic unit of encapsulation in C++. Its general form is as below:
class class_name : inheritance_list {
// private members by default
private:
// private members
protected:
// private members that can be inherited
public:
// public members
} object_list;
A class in C++ is a user-defined data type, which can hold its own data members and member functions in a block. In the class, the member data and functions can be stored in different access sections: private, protected, and public. The default access section for the class is private. The class is similar to a struct, but the default access section is the public in a struct.